In general, on a surface of a substrate such as a semiconductor wafer or a liquid crystal substrate, there is formed a wiring for forming a circuit on the surface. Such a wiring has been formed of copper having a low electrical resistance and a high reliability instead of aluminum. In general, a damascene method is used to form a Cu wiring on the substrate, and this method includes forming a recess such as via hole or trench for burying a wiring in an insulating film on the substrate by etching and burying the Cu wiring therein. Further, there has been made an attempt to enhance an EM tolerance of a semiconductor device by supplying a plating liquid containing CoWB (cobalt-tungsten-boron) or CoWP (cobalt-tungsten-phosphorous) to a surface of the substrate including the Cu wiring and by forming a metal film called a cap metal on the Cu wiring by electroless plating.
For example, in Patent Document 1, there is described a plating apparatus including a substrate rotation unit of rotating a substrate and a nozzle of discharging a plating liquid onto the substrate. In the plating apparatus described in Patent Document 1, since the plating liquid is supplied to the substrate being rotated, a uniform flow of the plating liquid is formed on a surface of the substrate. Thus, a plating process is uniformly performed on the entire surface of the substrate.
The electroless plating is known to be affected by reaction conditions such as a composition and a temperature of a plating liquid. Meanwhile, when the plating liquid is supplied to the substrate being rotated, the plating liquid flows from a central portion of the substrate toward a periphery portion thereof. Therefore, it is assumed that a temperature of the plating liquid on the substrate decreases as the plating liquid flows from the central portion of the substrate toward the periphery portion thereof. Therefore, the reaction conditions of the plating liquid are different between the central portion of the substrate and the periphery portion of the substrate. In order to suppress such non-uniformity of the reaction conditions, Patent Document 1 suggests a method of discharging a plating liquid while moving a nozzle between a central portion of a substrate and a periphery portion of the substrate.